Swelling-activated Ca2+ channels trigger Ca2+ signals in Merkel cells

Area of Science:

• Neuroscience
• Cell Biology
• Mechanobiology

Background:

• Merkel cell-neurite complexes are essential for fine touch sensation.
• Merkel cells are hypothesized to be mechanosensory, signaling via neurotransmission, but functional evidence is conflicting.

Purpose of the Study:

• To investigate if purified Merkel cells directly respond to mechanical stimulation.
• To elucidate the cellular mechanisms underlying Merkel cell mechanosensitivity.

Main Methods:

• Purified Merkel cells were subjected to anisotonic solutions to induce swelling.
• Calcium (Ca2+) imaging using fura-2 was employed to monitor cellular responses.
• RT-PCR was used to identify potential mechanotransduction ion channels.

Main Results:

• Hypotonic-induced cell swelling triggered Ca2+ transients in Merkel cells.
• These Ca2+ signals required extracellular Ca2+ influx and were modulated by internal Ca2+ stores.
• Voltage-activated Ca2+ channel (VACC) antagonists partially inhibited the Ca2+ transients.
• RT-PCR identified PKD1, PKD2, and TRPC1 transcripts in Merkel cells.

Conclusions:

• Merkel cells are directly activated by mechanical swelling, confirming their mechanosensory role.
• Swelling-activated Ca2+-permeable ion channels and intracellular Ca2+ release mediate these responses.
• These findings support the hypothesis that Merkel cells contribute to touch reception.